/* This is a public domain base64 implementation written by WEI Zhicheng. */

#include <stdio.h>

#include "base64er.h"

/* BASE 64 encode table */
static const char base64en[] = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I',
		'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W',
		'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k',
		'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y',
		'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/', };

#define BASE64_PAD	'='

#define BASE64DE_FIRST	'+'
#define BASE64DE_LAST	'z'
/* ASCII order for BASE 64 decode, -1 in unused character */
static const signed char base64de[] = {
/* '+', ',', '-', '.', '/', '0', '1', '2', */
62, -1, -1, -1, 63, 52, 53, 54,

/* '3', '4', '5', '6', '7', '8', '9', ':', */
55, 56, 57, 58, 59, 60, 61, -1,

/* ';', '<', '=', '>', '?', '@', 'A', 'B', */
-1, -1, -1, -1, -1, -1, 0, 1,

/* 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', */
2, 3, 4, 5, 6, 7, 8, 9,

/* 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', */
10, 11, 12, 13, 14, 15, 16, 17,

/* 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', */
18, 19, 20, 21, 22, 23, 24, 25,

/* '[', '\', ']', '^', '_', '`', 'a', 'b', */
-1, -1, -1, -1, -1, -1, 26, 27,

/* 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', */
28, 29, 30, 31, 32, 33, 34, 35,

/* 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', */
36, 37, 38, 39, 40, 41, 42, 43,

/* 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', */
44, 45, 46, 47, 48, 49, 50, 51, };

int base64_encode(const unsigned char *in, unsigned int inlen, char *out) {
	unsigned int i, j;

	for (i = j = 0; i < inlen; i++) {
		int s = i % 3; /* from 6/gcd(6, 8) */

		switch (s) {
		case 0:
			out[j++] = base64en[(in[i] >> 2) & 0x3F];
			continue;
		case 1:
			out[j++] =
					base64en[((in[i - 1] & 0x3) << 4) + ((in[i] >> 4) & 0xF)];
			continue;
		case 2:
			out[j++] =
					base64en[((in[i - 1] & 0xF) << 2) + ((in[i] >> 6) & 0x3)];
			out[j++] = base64en[in[i] & 0x3F];
		}
	}

	/* move back */
	i -= 1;

	/* check the last and add padding */
	if ((i % 3) == 0) {
		out[j++] = base64en[(in[i] & 0x3) << 4];
		out[j++] = BASE64_PAD;
		out[j++] = BASE64_PAD;
	} else if ((i % 3) == 1) {
		out[j++] = base64en[(in[i] & 0xF) << 2];
		out[j++] = BASE64_PAD;
	}

	return BASE64_OK;
}

int base64_decode(char *in, unsigned int inlen, unsigned char *out) {
	unsigned int i, j;

	for (i = j = 0; i < inlen; i++) {
		int c;
		int s = i % 4; /* from 8/gcd(6, 8) */

		if (in[i] == '=')
			return BASE64_OK;

		if (in[i] < BASE64DE_FIRST || in[i] > BASE64DE_LAST
				|| (c = base64de[in[i] - BASE64DE_FIRST]) == -1)
			return BASE64_INVALID;

		switch (s) {
		case 0:
			out[j] = ((unsigned int) c << 2) & 0xFF;
			continue;
		case 1:
			out[j++] += ((unsigned int) c >> 4) & 0x3;

			/* if not last char with padding */
			if (i < (inlen - 3) || in[inlen - 2] != '=')
				out[j] = ((unsigned int) c & 0xF) << 4;
			continue;
		case 2:
			out[j++] += ((unsigned int) c >> 2) & 0xF;

			/* if not last char with padding */
			if (i < (inlen - 2) || in[inlen - 1] != '=')
				out[j] = ((unsigned int) c & 0x3) << 6;
			continue;
		case 3:
			out[j++] += (unsigned char) c;
		}
	}

	return BASE64_OK;
}


